I might as well get this started. looking to replace the speakers in the rear, made by me, parcel shelf. I've currently got a pair of ancient Pioneer 8" three way speakers and am looking to upgrade. do 6x9s give a different sound to their circular cousins? and would seperate tweeters and mids (something like the Boston Acoustics ccomponent) be a better option quality wise. running the speakers from the headunit (sony cdx-m670), no external amps involved at the moment although that may be the next step.